ENJINKOZO

摘要

PURPOSE:To suppress the vibration and noise of an engine by forming at least a part of the sectional surface in a plane crossing at right angles with the crankshaft axis line of the side wall member of a ladder frame into a curved surface. CONSTITUTION:The side wall member 22 of a ladder frame 20 is formed into a curved surface in which the upper half part 22a is drawn so as to converge towards a cylinder center surface. The vibration shift in the direction perpendicular to the crankshaft axis line of the side wall member 22 is extremely effectively reduced for the vibration shift in the crankshaft axis line direction of a horizontal wall member 24. A thick beam part 22 extended in the nearly parallel direction to the crankshaft axis line is formed in the connection part between the upper and lower half parts 22a and 22b. Therefore, the vibration and noise of the engine can be suppressed.